At 6/19/2012 4:31:05 PM, Ahmed.M wrote:Q: What is the source of all new alleles?

Quite complicated actually. There are three ways it is created:

1) Mutations are random changes that occur in genes that can produce traits that have never been seen before in a species. While mutations are rare, productive mutations can result in profound changes after thousands of generations.

2) Sexual reproduction is another way to create different alleles. Chromosomes, or the strands that contain DNA, are split, broken and blended. When the sperm and egg combine, genes from both parents are blended randomly. The offspring comprise a unique mix of alleles.

3) Asexual bacteria are capable of genetic recombination, which means they can absorb bits of foreign DNA and incorporate it into their genetic code [source: http://curiosity.discovery.com... ].

1) Mutations are random changes that occur in genes that can produce traits that have never been seen before in a species. While mutations are rare, productive mutations can result in profound changes after thousands of generations.

2) Sexual reproduction is another way to create different alleles. Chromosomes, or the strands that contain DNA, are split, broken and blended. When the sperm and egg combine, genes from both parents are blended randomly. The offspring comprise a unique mix of alleles.

3) Asexual bacteria are capable of genetic recombination, which means they can absorb bits of foreign DNA and incorporate it into their genetic code [source: http://curiosity.discovery.com... ].

I don't think the source you stated is correct with regards to the source of all new alleles. In all honesty, I learned in my biology class that the source of all new alleles are mutations. Even your reputable source attests to this:

Mutations are almost always harmful. The only beneficial cases which still have numerous drawbacks in todays world that can arise from mutations (from what I know) is the case of sickle cell anemia for people in Africa who suffer from malaria. The person must have half of the disease and half regular hemoglobin.

Also there is a common misunderstanding of natural selection. Natural selection doesn't change an organism (e.g short giraffe neck to longer). The gene/trait must ALREADY exist within the gene pool/population. Let me give you an example:

--> Let us say you have a sandy environment with many brown beetles and very few green beetles, due to the advantage that the brown beetles have (camouflage) they are able to reproduce and survive better. However, over time the sandy environment changes to a lush green one. What happens is over time, the brown beetles die out and become few and the green beetles reproduce, populate and become the majority.

We can see in this example that the brown beetles didn't change from brown to green, the green beetle was ALREADY there and it simply reproduced and reproduced while the brown ones died off. This is natural selection.

1) Mutations are random changes that occur in genes that can produce traits that have never been seen before in a species. While mutations are rare, productive mutations can result in profound changes after thousands of generations.

2) Sexual reproduction is another way to create different alleles. Chromosomes, or the strands that contain DNA, are split, broken and blended. When the sperm and egg combine, genes from both parents are blended randomly. The offspring comprise a unique mix of alleles.

3) Asexual bacteria are capable of genetic recombination, which means they can absorb bits of foreign DNA and incorporate it into their genetic code [source: http://curiosity.discovery.com... ].

I don't think the source you stated is correct with regards to the source of all new alleles. In all honesty, I learned in my biology class that the source of all new alleles are mutations. Even your reputable source attests to this:

Mutations are almost always harmful. The only beneficial cases which still have numerous drawbacks in todays world that can arise from mutations (from what I know) is the case of sickle cell anemia for people in Africa who suffer from malaria. The person must have half of the disease and half regular hemoglobin.

Also there is a common misunderstanding of natural selection. Natural selection doesn't change an organism (e.g short giraffe neck to longer). The gene/trait must ALREADY exist within the gene pool/population. Let me give you an example:

--> Let us say you have a sandy environment with many brown beetles and very few green beetles, due to the advantage that the brown beetles have (camouflage) they are able to reproduce and survive better. However, over time the sandy environment changes to a lush green one. What happens is over time, the brown beetles die out and become few and the green beetles reproduce, populate and become the majority.

We can see in this example that the brown beetles didn't change from brown to green, the green beetle was ALREADY there and it simply reproduced and reproduced while the brown ones died off. This is natural selection.

There are several parts to Evolution.

First, there is variation. This is where new phenotypes come from.Second, there is differential reproduction (natural selection/artificial selection/genetic drift) of these phenotypes.

No one who has any grasp of biology thinks natural selection ought to create phenotypes. Oddly enough, you seem to think this is the common understanding of natural selection.

Variation in Evolutionary Theory is much more complicated than your high school/pre-high school understanding of mutation. Different genes have different functions. A large set of genes known as "regulatory genes" determine when to turn other genes on and off. Mutations in regulatory genes to can change the expression of homeoboxes in viable ways. Homeoboxes have been conserved through billions of years of evolution.

For instance, the eyes of fruit flies, mice, humans, and nearly every other bilateral creature is a result of mutations of regulatory genes that control the expression of Pax6. Pax6 itself has remained nearly identical for all that time. Duplications and mutations of Pax6 slowly lead to the development of new homeoboxes.

Viable variation in homeoboxes is very rare, but has been shown possible.

At 6/20/2012 12:25:55 AM, ScottyDouglas wrote:Why doesn't a fruitfly evolve considering we test them and they have generation after generation? Because we are watching?

Hmm....Even if, I suppose, no modification in the alleles of a species in an experimental setting occurs, then that may only contest the paradigm of the mechanism tested in evolution rather than the overall theory itself.

After all, there are multiple proposed mechanisms of Evolution that, with proper empirical justification, may be insufficient in explaining large-scale transformations.

"Homo sum, humani nihil a me alienum puto." --Terence

"I believe that the mind can be permanently profaned by the habit of attending to trivial things, so that all our thoughts shall be tinged with triviality."--Thoreau